Flexible compression member for a flexible pneumatic structural element and means for erecting pneumatic element structures

ABSTRACT

A flexible compression member ( 2 ) is essentially flat when a pneumatic structural element is in a slack state. When the pneumatic structural element is subjected to the action of pressure via a valve ( 3 ), the compression member ( 2 ) takes on a functionally curved shape similar to a segment of a cylinder. In the functional shape, the flexible compression member ( 2 ) has a greater geometrical moment of inertia and is supported by the skin ( 1 ) that is under pressure whereby considerably increasing the buckling load of the compression member ( 2 ). The ends of the compression member ( 2 ) lead into two node elements that can be joined together via joining elements. This enables the creation of pneumatic element structures and the erection thereof by using compressed air.

The present invention pertains to a pneumatic structural element in theform of an elongated air-tight hollow body that can be subjected topressure and comprises at least one compression member extending alongthe hollow body on the load side and at least two tight tension elementsthat are helicoidally looped around the hollow body in oppositedirections. In this case, the tension elements begin and end at nodeelements arranged on the ends of the least one compression member andare looped around the hollow body at least once.

Pneumatic structural elements of this type are generally known, forexample, from WO 01/73245.

In this case, the pneumatic structural element consists, for example, ofa flexible gas-tight hollow body that is reinforced with a textilematerial. At least one dimensionally stable compression member extendingalong a surface line is arranged on the outer side of this hollow bodyin such a way that it is supported by the hollow body and cannot buckle.Two tension elements are fixed on the ends of this compression member,wherein said tension elements are helicoidally looped around theessentially tubular hollow body once in opposite directions andintersect on a surface line of the hollow body that lies opposite of thecompression member, namely in the longitudinal center of the hollowbody. Node elements are situated at the locations at which thecompression member is connected to the tension elements, wherein thebearing forces are also introduced into said node elements.

The pneumatic structural element disclosed in WO 01/73245 has variousdisadvantages that manifest themselves in practical applications: inorder to transport and install the compression member, the excessivelength thereof makes it necessary to disassemble the compression memberinto individual parts that are, for example, butt-jointed at theconstruction site. This also requires the insertion of the individualparts into brackets provided for this purpose. The installation andtightening of the tension elements also needs to be carried out at theconstruction site in this case. Since the tension elements and thecompression members need to be installed into corresponding nodeelements suitable for absorbing tensile forces, compressive forces andbearing forces, the installation expenditures at the construction siteare comparatively high.

The present invention is based on the objective of developing apneumatic structural element that can be erected at a construction sitewithout noteworthy installation expenditures.

This objective is attained with the characteristics disclosed inindependent Claims 1, 14, 15 and 18, wherein advantageous additionaldevelopments of the invention form the objects of the remaining claims.

The object of the invention is described in greater detail below withreference to the enclosed figures.

The figures show:

FIG. 1 a, a cross section through a flexible pneumatic structuralelement according to the invention in the deflated state;

FIG. 1 b, the pneumatic structural element according to FIG. 1 a with afirst embodiment of a compression member in the pressurized state;

FIG. 2, a side view of a pneumatic structural element in the empty,rolled-up state;

FIG. 3, a cross section through a second embodiment of a compressionmember;

FIG. 4, a cross section through a third embodiment of a compressionmember;

FIG. 5, a cross section through a fourth embodiment of a compressionmember;

FIG. 6, a variation of the fourth embodiment;

FIG. 7, a side view of a node element with a compression member;

FIG. 8, a cross section through a fifth embodiment of a compressionmember;

FIG. 9, a cross section through a sixth embodiment of a compressionmember;

FIG. 10, a side view of a node element with two compression members;

FIG. 11, an isometric projection of one exemplary application for theflexible pneumatic structural element according to the invention;

FIG. 12, an isometric projection of a flexible pneumatic structuralelement with a connecting element;

FIG. 13 a, a side view of two pneumatic structural elements with aconnecting element in the slack state, and

FIG. 13 b, a side view of two pneumatic structural elements with aconnecting element in the pressurized state.

Cross sections of the flexible pneumatic structural element according tothe invention are illustrated in FIGS. 1 a, b, namely in the slack statein FIG. 1 a and in the pressurized state in FIG. 1 b. The pneumaticstructural element consists of a flexible shell 1, onto one side ofwhich a compression member 2 in the form of a flexible plate ofcompression-proof material is attached over its entire surface, forexample, by means of bonding. The shell 1 consists, for example, of aplastic material that is reinforced with a textile material and bondedor welded shut in a gas-tight fashion. Another embodiment of the shell 1can be realized by embedding a gas-tight tube of an elastic plasticmaterial—for example, polyurethane—in a tube of a textile material withlimited stretchability—for example, aramid fibers.

In the deflated state, the compression member 2 is essentially flat suchthat the pneumatic structural element can be rolled up and transportedin the rolled-up state as shown in FIG. 2. When the deflated andslack—and possibly rolled-up—pneumatic structural element is filled withcompressed air via a valve 3, it initially unrolls and slowly assumesthe cross-sectional shape shown in FIG. 1 b in the unrolled state, inwhich it is still slack. During this process, the compression member 2is bent into the functional shape of a cylinder segment shown in thefigure. The stability of the elastically bendable compression member inits functional shape essentially has two reasons: first, the bentfunctional shape increases the geometrical moment of inertia of thecompression member. Second, the compression member is supported radiallyreferred to its longitudinal axis on a pneumatic spring due to theinteraction with the tension elements and the pressurized shell 1, i.e.,the compression member is not freely suspended between its ends. Thebuckling load of the compression member is significantly increased dueto the higher geometrical moment of inertia in connection with thesupport of the compression member on a pneumatic spring. A tangentialstress au is simultaneously built up on the shell 1, wherein thefollowing applies:σ_(u) =p·R[N/m]

-   p=internal pressure of the pneumatic structural element [N/m²]-   R=radius of the pneumatic structural element [m]

The adhesive connection between the compression member 2 and the shell 1causes this tensile stress au to be transmitted onto the compressionmember 2, namely in such a way that the compression member is alsostressed to au. This additionally increases the geometrical moment ofinertia of the compression member, as well as the buckling load.

Variations for designing the compression member 2 and for increasing thebuckling load are illustrated in FIGS. 3-6. In the variation shown inFIG. 3, the compression member 2 is arranged within a flexible shell 1and consists of a gas-tight hollow body 4. Analogous to the embodimentshown in FIGS. 1, 2, this hollow body is elastically bendable, but alsoable to absorb longitudinally directed compressive forces. The hollowbody 4 is composed, for example, of two plates 6 with the aforementionedproperties that are flatly bonded or welded to one another along theiredges. If the hollow body 4 is pressurized by means of a pressure mediumuntil a pressure p₁ is reached and the pressure in the interior of theflexible shell is adjusted to p₀<p₁, the tubular compression memberproduced by the hollow body 4 is able to absorb longitudinally actingcompressive forces without buckling.

FIG. 4 shows another means for increasing the geometrical moment ofinertia of the compression member 2. Alternatively to FIG. 1,the—initially—flat compression member 2 is arranged in the interior ofthe flexible shell 1, namely by means of welding or bonding. A web 7 ishinged to an elastic joint 5 that centrally extends over the entirelength of the compression member. In the non-pressurized state of thepneumatic structural element according to the invention, the web 7 liesessentially parallel to the plate 6 of the compression member 2. Aplurality of filaments 8 transversely extends through the flexible shell1; in the non-pressurized state of the flexible shell 1, the filaments 8remain loose. In the pressurized state of the flexible shell 1, however,the filaments are tightened to such a degree that the pressure built upin the flexible shell 1 causes the web 7 to be displaced from itsoriginal position into the position shown in FIG. 4, in which itessentially stands vertically on the plate of the compression member 6.

FIGS. 5 and 6 show two variations of another arrangement for increasingthe geometrical moment of inertia. In both variations, several flexibleand gas-tight tubular shells, for example, five shells 9, are placed onand attached to the plate 6 of the compression member 2. Equallyflexible plates 6 are inserted into the shells 9 and connected to therespective shells 9. When the shells 9 are subjected to pressure, theplates 6 are bent up such that the geometrical moment of inertia of thecompression member 2 shown in FIGS. 5, 6 is increased. The differencebetween FIGS. 5 and 6 can be seen in the arrangement of the thuslydesigned compression member 2: the compression member is arrangedoutside the flexible shell 1 in FIG. 5 and inside the flexible shell inFIG. 6. Consequently, the condition p₁>p₀ also applies to the embodimentaccording to FIG. 6.

Although not illustrated in the figures, the invention also makes itpossible to utilize a multilayer shell 1. The scope of the inventionalso includes embodiments, in which the compression members are arrangedbetween different layers of the shell 1.

FIG. 7 shows a first embodiment of a node element 11. The effects of thebearing force, the compressive force in the compression member 2 and thetensile forces in the tension elements 12 are vectorially reduced tozero. The node element 11 shown contains a deep eye 13 for beingnon-rotationally anchored in a (not-shown) support construction. Thenode element 11, the compression member 2 and the tension elements 12are connected to one another with conventional means known from thefield of mechanical engineering.

FIG. 8 shows a pneumatic structural element with two compression members2 that are arranged along opposite surface lines of the flexible shell1. The characterizing features described with reference to FIGS. 1 a, balso apply in this case—with the exception of the second compressionmember 2. A thusly designed pneumatic structural element is providedwith at least one pair of tension elements 12 per compression member 2,wherein the tension elements are respectively looped helicoidally aroundthe pneumatic structural element at least once in opposite directions.The arrangement of eyes 13 naturally can be adapted to the respectiverequirements as long as the zero-sum condition is fulfilled. Forexample, the eyes 13 may also be arranged such that the longitudinalaxis of one eye 13 intersects the longitudinal axis of the pneumaticstructural element or lies below this latter longitudinal axis.

If a pneumatic structural element with two compression members 2 needsto be realized in accordance with the embodiment shown in FIGS. 3, 4, 5or 6, it is possible to simply provide two compression members designedin accordance with these embodiments as shown in FIG. 9: in this case, adouble arrangement of the compression member 2 with the hinged web 7 isprovided. The opposing web 7 rather than the surface line facing thecompression member 2 is used as the connecting point for the filaments 8that move the webs 7 into the upright position under the influence ofthe pressure medium. The features of the pneumatic structural elementdescribed with reference to FIGS. 1 a, b and 2 consequently are alsoachieved in this case.

An embodiment of a node element 14 for receiving two compression members2 is shown in FIG. 10. The compression members 2, at least one pair oftension elements 12 per compression member—and naturally the flexibleshell 1—as well as devices for absorbing the bearing forces, forexample, the eyes 13, are combined in this node element. The arrangementof the eyes 13 once again has a purely exemplary character and shouldnot be understood in a restrictive sense.

FIG. 11 shows the utilization of several pneumatic structural elementsaccording to the invention, for example, as shown in the FIG. 10, forconstructing a pneumatic and essentially self-erecting elementstructure, in this case a framework for a roof. In the embodiment shownin FIG. 11, 18 pneumatic structural elements of essentially identicaldesign are suitably connected to one another. This is realized, forexample, with the connecting elements 15 that are shown in FIG. 12 anddescribed further below. Several pneumatic structural elements can becombined in such a connecting element 15 with their node elements 14 orin an actual node.

In the embodiment shown in FIG. 11, three to four pneumatic structuralelements are respectively connected in one connecting element 15. Theends of the pneumatic structural elements that stand on the ground inFIG. 11 may be equipped with a shoe instead of a node element 15. Theelement structure according to FIG. 11 can be covered with a suitablecanvas or tarpaulin either before or after its erection. FIG. 12 showsan embodiment of the connecting element 15 that serves for connectingfour pneumatic structural elements. These pneumatic structural elementsmay be realized with two compression members 2 as shown in FIG. 12. Thelower eyes 13 can be eliminated in an embodiment with only onecompression member. Four eyes 16 are provided per pneumatic structuralelement to be connected, namely two respective eyes in the form of acoaxial arrangement, through which a bolt 17 is inserted.

The connecting element 15 may be realized in the form of a welded sheetmetal construction or a casting.

The angle between two flexible pneumatic structural elements in theirfunctional shape can be defined by the arrangement of the upper eyes 16relative to the lower eyes. This also defines the outside contour of astructure composed of flexible pneumatic structural elements.

FIGS. 13 a, b show steps for assembling such a structure: two pneumaticstructural elements are connected to a first connecting element, forexample, the connecting element in the gable of the structure shown inFIG. 11, with the aid of the bolts 17 after the still slack pneumaticstructural elements were unrolled. Other connecting elements andpneumatic structural elements can be installed in the same step. Thepneumatic structural elements are then pressurized such that thecompression members assume their functional shape. Consequently, theyare able to absorb the moments built up in the connecting elements suchthat the entire structure is erected as indicated by the correspondingarrows in FIG. 13 b.

1. A flexible pneumatic structural element comprising an elongated air-tight hollow body that can be subjected to pressure; wherein at least one pair of tight tension elements helicoidally looped around the hollow body in respectively opposite directions on each compression member; two node elements provided respectively per compression member; the compression member being elastically bendable, having a plate-like shape, rigidly connected to a shell; the compression member being flat and adapted to be rolled up in a deflated state of the pneumatic structural element; and, the compression member being bent and essentially assuming a shape of a cylinder segment in an inflated, pressurized state of the pneumatic structural element such that the pressurized shell stabilizes the compression member in this shape.
 2. The flexible pneumatic structural element according to claim 1, wherein a connection between the compression member and the shell is realized such that the stress σ_(u) of the shell is transmitted onto the compression member.
 3. The flexible pneumatic structural element according to claim 2, wherein the compression member is bonded to the shell or connected to the shell by means of welding over its entire surface.
 4. The flexible pneumatic structural element according to claim 3, wherein the compression member increasingly unrolls and assumes its stretched, functional shape as the pressure being built up in the shell increases.
 5. The flexible pneumatic structural element according to claim 4, wherein the compression member is designed such that its buckling load is increased.
 6. The flexible pneumatic structural element according to claim 5, wherein the compression member is composed of two plates that form the hollow body, wherein when the hollow body is subjected to a pressure p₁>p₂, the compression member assumes a tubular shape.
 7. The flexible pneumatic structural element according to claim 5, wherein the compression member is provided with an elastic joint that centrally extends over an entire length of the compression member and to which a web is hinged, wherein the web is connected to the shell in the region of a surface line lying opposite of the elastic joint by means of a plurality of filaments.
 8. The flexible pneumatic structural element according to claim 5, further comprising: at least one tubular shell is arranged on the plate of the compression member; and an elastically bendable plate arranged on an inner side of the tubular shell and bends up when the shell is pressurized.
 9. The flexible pneumatic structural element according to claim 1, wherein multiple compression members are arranged on the shell.
 10. The flexible pneumatic structural element according to claim 9, wherein at least one compression member is arranged within the shell.
 11. The flexible pneumatic structural element according to claim 9, wherein at least one compression member is arranged on an outside of the shell.
 12. The flexible pneumatic structural element according to claim 9, wherein at least one compression member is arranged between different layers of the shell.
 13. The flexible pneumatic structural element according to claim 1, wherein the two node elements can be attached to connecting elements.
 14. The flexible pneumatic structural element according to claim 1, wherein the two node elements are provided with at least one eye, through which a bolt of a non-rotatable mounting arrangement can be respectively inserted.
 15. The pneumatic element structure element according to claim 1 further comprising: flexible pneumatic structural elements, the flexible pneumatic structural elements are connected by means of connecting elements; and wherein the pneumatic element structure is automatically erected and assumes a predetermined shape when the flexible pneumatic structural elements are subjected to pressure.
 16. The pneumatic element structure according to claim 15, wherein the connecting elements for the flexible pneumatic structural elements comprises: means for mounting at least two node elements; and mounting means that are realized such that the flexible pneumatic structural elements are arranged at a predetermined angle relative to one another in their functional shape.
 17. The pneumatic element structure according to claim 16, wherein the connecting elements are provided with pairs of coaxial eyes between which one respective node element with an eye can be non-rotationally mounted by inserting a bolt.
 18. The pneumatic element structure according to claim 16, wherein the connecting elements are provided with at least two upper and two lower pairs of coaxial eyes, wherein the position of the upper pairs relative to the lower pairs defines an angle between the flexible pneumatic structural elements in their functional shape. 